Is a 20 amp breaker 120 or 240?

A 20 amp breaker can be either. Amps and volts are independent: the 20 sets how much current trips it, and the number of poles sets the voltage. Single-pole is 120V; double-pole, taking two spaces with tied handles, is 240V.

Most 20 amp breakers in a home panel are single-pole 120V for receptacles and lights. A 20 amp double-pole shows up for small 240V loads like a compressor or baseboard heater.

You can read it at a glance: one space and one handle, 120. Two spaces, tied handles, 240.

An outlet does not convert anything either way; a 240V circuit needs 240-rated receptacles and the right plug pattern.

Wiring a 240V circuit? The 240 volt wire gauge calculator pairs the breaker with the conductor it needs.